Aside from sound, the most important element in the selection of an instrument is likely to be the feel of the action. Unless you're considering only digital pianos that employ an actual acoustic action (see "Hybrid Pianos," elsewhere in this issue), you'll be selecting from a variety of actions that all try to emulate the feel of an acoustic action. The aspect of action feel that seems to generate the most discussion is whether the touch weight is light or heavy, and which is better. This is covered in more detail in "Digital Piano Basics, Part 1," but here's the bottom line: Just as there is no single correct piano sound, there is no single correct touch weight; rather, there is a range of acceptable touch weights. If you spend the majority of your playing time with a heavy action, when you encounter an instrument with a lighter action, be it acoustic or digital, you'll play too heavily — and vice versa. The only cure is to play as many instruments as possible, as often as possible. Listen to how each piano responds and adjust your touch accordingly. You've probably driven cars with light steering and cars with heavy steering, and generally managed to avoid hitting any trees with either of them. With varied experience, you learn to adapt.
Common to acoustic and digital actions is mechanical noise. Digitals are frequently accused of having noisier actions because their sound can be reduced to a whisper or played through headphones, leaving the action noise audible, whereas the sound of an acoustic piano tends to always mask its action noise. This is not to say that some digital actions aren't unusually noisy, but to honestly compare them, you have to play them with the volume turned off. In addition to letting you compare action noise, this prevents your mind from judging the feel of an action based on the tone of the instrument.
New or Used?
Because digital technology advances at a blistering pace relative to acoustic-piano technology, there is much less interest in used digitals than in used acoustics. Many of today's digital pianos eclipse the capabilities of the models of even five years ago. Combine this technological advancement with the fact that support of older instruments may be limited — after production of a particular model ceases, electronics manufacturers are required to maintain replacement parts for only seven years — and investing in older models becomes worthy of serious second thoughts.
Owner's manuals no longer accompany many used instruments. If you find an interesting used instrument, make sure that the manual is either still with it, or is readily available from the manufacturer or on the Internet. The manual is your best tool for ensuring that everything on the instrument still works correctly. It's not simply a matter of pressing every key, button, and pedal to see that they work; to thoroughly check the instrument, you also need to know what some of the less obvious controls are supposed to do. None of this is to say that used instruments should be avoided — I've played ten-year-old digital pianos that worked perfectly. But when considering an older digital piano, extra care should be exercised.
Your shopping options depend on the type of digital piano you've decided to buy and the region you live in. In North America, different categories of instruments are available through different types of outlets. Furniture-style models, particularly the higher-end models manufactured by the largest suppliers, are available only through traditional bricks-and-mortar piano or full-line music retailers. The lower-priced furniture-style, slab, or stage models, and some of the less widely distributed brands, are available from a cross section of traditional bricks-and-mortar music retailers, club and warehouse chains such as Costco, consumer-electronics chains such as Best Buy, and online retailers.